1. Field of the Invention
The present invention relates to an original conveying apparatus having an original travel reverse apparatus, and more particularly, it relates to a sheet original conveying apparatus in which a sheet original is conveyed to a predetermined position in an image reading portion and is set at that position.
2. Related Background Art
In the past, there have generally been proposed two methods for conveying a both-face imaged original in an original apparatus. In one of such methods, an original is reciprocated between a platen glass (referred to as "platen" hereinafter) and a reverse convey path by several times to reversely rotate a travelling direction (travel) of the original (first type method). In the other methods, after an original is reversed in a reverse convey path, the original is rested on a platen (second type method). (Hereinbelow, the word "reverse" means reverse in the travelling direction).
The first type method operates as follows. That is to say, after the original on a tray was once conveyed to the platen, the original is immediately conveyed to the reverse convey path without effecting a reading operation, where the original is reversed. Then, the original is returned to the platen, where the original is read from its second surface. After an image regarding the second surface was formed, the original is reversed again in the reverse convey path and then is returned to the platen, where a first surface of the original is read. After an image reading the first surface was formed, the original is discharged. After the original is discharged, a next original is conveyed to the platen, and the similar operation is repeated.
The second type method is disclosed in Japanese Patent Laid-Open No. 4-116071, for example, and an operation thereof is schematically shown in FIG. 43A. In FIG. 43A, when a both-face copy is obtained from a both-face imaged original, the original is directed from an original tray 504 to first and second convey paths 501, 502, and, as shown in FIG. 43B, when a trail end of the original leaves a junction A between the first and second convey paths 501 and 502, a flapper 506 is switched toward a convey path 503. As shown in FIG. 43C, the original P1 is conveyed in a reverse direction onto a platen 510. As shown in FIG. 43D, when the trail end of the original P1 passes through the junction A, the flapper 506 is switched toward the convey path 502, and a succeeding original P2 is directed to the convey path 502, where the original P2 is reversed. Then, the original P2 is directed to the convey path 503 and is conveyed onto the platen 510, as is in the original P1.
Regarding other originals, the similar operation is repeated successively so that the original is read from its second surface and then is returned to the original tray. A sheet on which an image regarding the second surface was formed is discharged on an intermediate tray of a copying machine temporarily. After the second surfaces of all originals were read, the originals are supplied again from the lowermost one, and, as is in the second surface, the original is reversed to read a first surface of the original. In this case, the sheet (transfer sheet) is supplied from the intermediate tray. As a result, the images are formed on both surfaces of the transfer sheet.
However, in the above-mentioned conventional techniques, there have been the following drawbacks regarding the image formation of the both-face imaged original.
In the first type method, since the original is returned and reversed after the original is once conveyed to the platen, it takes a long time to exchange the original, thereby worsening productivity.
In the second type method, the productivity can be improved since the exchange of the original can be effected for a short time and the original can be circulated. However, the following drawbacks occur.
(1) Since major part of the convey path is commonly used both in a one-face original convey mode and in a both-face original convey mode, the common convey path becomes long, with the result that it takes a long time to convey the original in the one-face original convey mode. Thus, in order to maintain the proper productivity, the original must be conveyed at a high speed.
(2) Since the original reverse path extends toward the platen, when a longer original is reversed, a tip end of the longer original enters into the convey path on the platen. Thus, during the image formation of the preceding original, the succeeding original cannot be reversed. In order to solve this problem, the reverse path must be longer, with the result that not only the entire apparatus becomes bulky but also the original conveying time in the one-face original convey mode becomes longer.